When a communication session is in a stable state in the internet protocol multimedia subsystem (IMS) network that provides voice over wireless (e.g., voice over long term evolution) communication services, a set of virtual network functions maintains the session state for the ongoing communication session. Thus, actions associated with the communication session traverse the same virtual network functions. For example, a 3GPP multiple media telephony application server (MMTel-AS or referred herein as TAS) maintains the state of a stable communication session for which the Session Initiation Protocol (SIP) is used to establish it. If the communication session was part of a three-way call and one of the call legs is to be removed from the call, a SIP Bye message would be sent from the user equipment (UE) to have that call leg removed. Conventionally the Bye message needs to traverse the TAS so it may maintain control of the call and update the call state. If the TAS VNF is shutdown from service, the call state may not be updated which may result in improper call handling (e.g., call detail recording used for billing may not correctly reflect the call duration).
This disclosure is directed to addressing issues in the existing technology.